The present proposal is the continuation of the annual follow-up of a cohort of children age 5-9 years and their family members. The objective of the study is to identify factors for obstructive airways disease which operate early in life. No strikingly new data have been generated since the previous summary. Efforts have been focused on solving methodologic problems encountered in the analysis of rates of change in pulmonary function in children during puberty. Once these problems have been solved, analysis will focus on the epidemiologic characteristics of children at various levels of growth of lung function. These analyses will be based upon 5 years of observation of the cohort.